Initially teeth wobbling, order a brace (3)
I believe the answer is:
two
'a brace' is the definition.
(I've seen this before)
'initially teeth wobbling order' is the wordplay.
'initially' says to take the initial letters.
The first letters of 'teeth wobbling order' is 'TWO'.
(Other definitions for two that I've seen before include "Number in pair" , "''... turtle doves''" , "Company, so it's said" , "not very many" , "Cat's coat" .)